00/01597 Mine explosions and characteristics of remediation of their consequences

Abstract

Pyrolysis and oxidation products of n-tetradecane combustion have been analyzed in a direct injection diesel engine at two different air/fuel feed ratios by in-cylinder fast sampling and analysis of the combustion products during the engine cycle.The early and efficient transformation of n-tetradecane in fuel-rich conditions was shown by the rapid rise of CO and CO2, the low concentration of unburned fuel, and the massive formation of light hydrocarbons (C2H2, C2H4). On the other hand a higher concentration of unburned n-tetradecane and a lower and delayed formation of CO2 and light hydrocarbons (mainly CH4 and C2H6) in fuel-lean conditions indicated the relatively low temperature that hinders the rapid oxidation of the fuel. For both air/fuel ratios the concentration of identified unsubstituted polycyclic aromatic hydrocarbons (PAH) increases during the engine cycle and reaches its peak value before the maximum of soot concentration. The formation of soot and PAH was greater in fuel-rich conditions than in fuel-lean ones.The effect of fuel aromatic content on combustion process and particularly on soot and PAH formation was studied by burning a n-tetradecane/α-methylnaphthalene mixture (90/10 vol. %). The addition of α-methylnaphthalene to n-tetradecane, although it did not change the overall characteristics of the combustion process, favoured the pyrolysis of the fuel. The formation in fuel-lean conditions of CO and C2H2 caused by the presence of α-methylnaphthalene can be explained by the peculiar mechanism of α-methylnaphthalene oxidation. The formation of soot and PAH also increased; this can be attributed to a larger formation of C2H2 and aromatic radicals which are considered precursors in the soot formation process.